1. Field of the Invention
The present invention relates to pistons in an internal combustion engine and more particularly to a piston ring for a piston.
2. Description of the Related Art
DE 195 01 792 C2 describes a piston with a piston ring being designed especially for the specific conditions of a flat piston. For this purpose, the piston ring has a width which is greater than a circumferential surface of the piston, so that there is an axially projecting length, which is shaped into a spring end, and which is supported on a top side of the piston.
All the embodiments of DE 195 01 792 C2 have a circular-arc-shaped transition which is greater than 180.degree.. One embodiment, shown in FIG. 3, has a bent-over spring end which comes to bear with its face on the top side of the piston. Some disadvantages are associated with this under unfavorable conditions. Thus, in the case of a piston ring subjected to high loading, the bent-over spring end may turn in further in the direction of the inside of the piston ring, which can result in the piston ring loading itself. Furthermore, leakages may occur on the inside of the piston ring, and these leakages, although not serious, can be measured in a damping-force chart.
Particular loads always occur at a piston ring when the piston ring is used with a piston for a piston-cylinder unit having grooves in the cylinder. The piston ring is deformed in the direction of the groove root and may possibly be squeezed at the runout of the groove. The piston disclosed in DE 36 11 288 A1 therefore has a guide ring for the radial guidance of the piston and a piston ring, and which performs the sealing function. In this complicated solution too, however, the limits of loading in modern vehicles is reached.